Glass compositions based on tungsten, molybdenum, and/or vanadium oxides, and opto-electronic components embodying such glasses
Silica, boric oxide and phosphoric oxide are commonly recognized as glass-forming oxides. In contrast, oxides of tungsten and molybdenum are generally regarded as glass-modifying oxides, rather than glass-forming oxides.
In the case of tungsten and molybdenum, this is due, in part, to the propensity of the W6+and Mo6+ions to be octahedrally, rather than tetrahedrally, coordinated by oxygen (O). Consequently, the ion tends to act as a network modifying species.
Melts in silicate and borate systems that are rich in these oxides tend to crystallize spontaneously during cooling. However, corresponding melts in phosphate and tellurite systems that are rich in these oxides can be quenched at reasonable rates to the glassy state. This is particularly true if an alkali metal oxide is included in the melt.
Binary glasses in alkali metal tungstate, molybdate and vanadate composition systems have been melted and formed by employing unusually rapid quenching methods. Such glasses are of practical interest because of their unusual electrical properties, including high ionic conductivity, and electrochromic properties. However, their use has been severely limited by their marginal stability. This not only makes production of the glass difficult, but essentially makes it impossible to form bulk bodies, or articles of a practical size, from the glass.
It is then a basic purpose of the present invention to provide relatively stable tungstate, molybdate and vanadate glasses, that is, glasses having tungsten and/or molybdenum and/or vanadium oxides as glass-forming oxides.
It is a further purpose to provide tungstate, molybdate and vanadate glasses that can be melted and shaped in a practical manner.
Another purpose is to provide a component for a telecommunications system that is produced from a tungstate, molybdate, or vanadate glass.
To this end, it is a purpose to provide a tungstate, molybdate, or vanadate base glass that is completely transparent, or at least transparent to a useful degree, in the visible, as well as in the near infra-red, portions of the spectrum.
The invention resides in part in alkali tungstate, molybdate and vanadate glasses, the compositions of which consist essentially of 15-70 mol % of at least one oxide selected from the group consisting of WO3, MoO3, VO2.5, 0-35% CrO3, 0-15% UO3, the total content of WO3 plus MoO3 plus VO2.5 plus CrO3 plus UO3 being 50-70%, 20-50% R2O where R represents at least two elements selected from the group consisting of Li, Na, K, Rb, and Cs, Ag and TI, optionally, 0-10% MO where M is an element selected from the group consisting Mg, Ca, Sr, Ba, Zn, Cd, and Pb, 0-5% X2O3 where x is at least one element selected from the group consisting of Al, Ga, In and Bi, 0-5% of at least one transition metal oxide, 0-15% P2O5 and/or TeO2, and 0-5% of an oxide of a rare earth metal in the lanthanide series.
The invention further resides in a component for a telecommunications system embodying a glass having a composition which consists essentially of 15-70 mol percent of at least one oxide selected from the group consisting of WO3, MoO3, VO2.5, 0-35% CrO3, 0-15% UO3, the total content of WO3 plus MoO3 plus VO2.5 plus CrO3 plus UO3 being 50-70%, 20-50% R2O where R represents at least two elements selected from the group consisting of Li, Na, K, Rb, and Cs, Ag and TI, and, optionally, 0-10% MO where M is an element selected from the group consisting of Mg, Ca, Sr, Ba, Zn, Cd, and Pb, 0-5% X2O3 where x is at least one element selected from the group consisting of Al, Ga, In and Bi, 0-5% of at least one transition metal oxide, 0-15% P2O5 and/or TeO2, and 0-5% of an oxide of a rare earth metal of the lanthanide series.
The invention further resides in a method of producing a stable alkali tungstate, molybdate, or vanadate glass which comprises incorporating sources of at least two alkali metal oxides in the glass batch as modifying oxides.